Identification And Characterization Of Candida Albicans FOL1and FOL2Genes

Folic acid can be converted to tetrahydrofolate in vivo, which is essentialcofactors in one-carbon (C1) transfer reactions and required for the synthesis ofcompounds such as methionine and purines. Candida albicans is an important clinicalfungal pathogens. The open reading frames of CaFOL1and CaFOL2genes are2367bp and831bp in length, and encode proteins of788and276amino acids, respectively.In order to the study the functions of CaFOL1and CaFOL2genes in thetetrahydrofolate synthesis pathway, we used the URA-BLASTER approach toconstruct heterozygous and homozygous mutants for the CaFOL1and CaFOL2genes.Phenotype analysis indicates that the homozygous mutant for CaFOL1(fol2△/fol2△) can not survive in media without exogenously supplemented folic acid. We clonedthe CaFOL2gene into the Candida albicans expression vector pCR4, and thentransformed this plasmid into the homozygous mutant for CaFOL2. This mutantcontaining the pCR4-CaFOL2plasmid could grow in media without supplementedfolic acid. Therefore, CaFOL2is required for C. albicans tetrahydrofolatebiosynthetic pathway. However, we failed to obtain any homozygous mutant forCaFOL1in media with supplemented folic acid after repeated trials. This suggeststhat the homozygous mutant for CaFOL1(fol1△/fol1△) might not survive even inmedia with supplemented folic acid. Therefore, CaFOL1might be an essential genefor the growth of Candida albicans.